The older Gold Cups were hand fitted, and they were very good 1911s, some of the best guns to ever roll out of the Colt factory without a doubt. In the 70s quality started to go downhill at Colt, by the late 70s there wasn't nearly as much work going into the Gold Cups as before, sadly they were really pretty average guns, and have remained so until today. Quality has come up in very recent years at Colt, I still don't think they're at that 60s/early 70s level though, especially with the Gold Cups.
If you have to own a series 70 Gold Cup, shoot for an early 70s model. I personally like the pre series 70 Gold Cups, often reffered to as just National Match models because of the lack of a Gold Cup rollmark. Here's my 62 model which is one my favorite 1911s.
With closer examination you'd see the frame rails were obviously peened on these old models, which is indicative of extra fitting, and ensures a tight slide to frame fit, not something you'll see on a later GC. Bushings were also tight on these models as well, and the triggers were just amazing, my 62s trigger is every bit as good my Les Baer's. The bluing was amazing too, better than nearly anything you'll see today in fact.
The old GCs were fantastic, probably my favorite Colt models ever, and they rival some of the best production level 1911s available today in quality. Overall, I don't think they're quite up to a DW Valor, or TRP, but they're very close, and they blow those away from a collectability and styling standpoint IMO.